This follow-up study to ACTG 175 will determine the influence of virus load, CD4 cell counts, biologic phenotype, and the presence of symptomatic HIV disease on the response to a new therapeutic regimen, on the kinetics of viral replication, and on the rate of emergence of 3TC-associated resistance mutation at codon 184. It will compare the efficacy of continuing ZDV/ddI or ZDV/ddC versus adding 3TC or switching to ZDV/3TC. M01RR000960490 The primary objective of this study is to determine whether Panorex, a monoclonal antibody against glycoproteins on the cell surface of adenocarcinomas, given in combination with 5-FU based chemotherapy improves survival relative to 5-FU-based chemotherapy alone in patients with surgically resected stage III (Duke's C) adenocarcinoma of the colon.